Air intakes that centrifugally separate heavier-than-air particles from the air to be used in internal combustion engines, ventilation systems, and other apparatus that draw in air laden with debris, are known. The use of in-line filters in air delivery systems to clean the air is also, per se, known. However, air filters are subject to plugging by debris from the air passing through the filter, which eventually increases the restriction to airflow through the filter and decreases the operating performance of an associated device, such as an electronically controlled internal combustion engine being supplied with air through the filter. Frequent filter replacement and shorter service intervals may also be required, which increases the cost of operation.
Examples of assignee's prior powered air cleaning systems and air cleaning methods are shown in U.S. Pat. Nos. 7,056,368; 6,425,943; 6,406,506; 6,338,745 and 6,319,304. The motors of the motor-driven fans in these known powered air cleaning systems are run at a single rated speed, around 3200 rpm. The clean airflow rate from such a system operating at this single rated speed must satisfy the maximum airflow requirement of the device being supplied with clean air by the system. When the airflow requirement of a device is reduced to less than the maximum airflow requirement, there is an inefficiency in that the air cleaning system continues to operate to satisfy the maximum airflow requirement of the device. Thus, there is excess airflow provided by the system which flows through the system to atmosphere with the debris laden air through the ejector port(s) in the separator ejector chamber(s) of the system.
The powered air cleaning system of U.S. Pat. No. 7,056,368 is operated to maintain a positive pressure in the separator-ejector chamber upstream of a filter in the system, but only provides an essentially neutral pressure at the clean air outlet of the system through which clean air is provided to a device such as an engine or ventilation system. The device itself may have an air filter through which the incoming clean air from the system is passed. The air filter of the device is also subject to plugging by any debris remaining in the clean air from the system and requires periodic replacement. An improved powered air cleaning system and air cleaning method having greater operational efficiency and higher performance in air cleaning and in relation to the operation of a device downstream of the system, capable of efficiently meeting varying airflow requirements of the device and increasing filter change intervals for filters in the device downstream of the system, are needed.
For this purpose, a powered air cleaning system of the present invention comprises a flow path extending through the system from an inlet to an outlet, a motor-driven fan located along the flow path to draw particulate debris laden air into the inlet and rotate it about an axis to form a rotating flow that stratifies the debris laden air with the heaviest particles in the outermost orbits of the rotating flow, an ejector port for ejecting particulate debris laden air from the stratified rotating flow in the system, and at least one de-swirl blade located within the rotating flow for aerodynamically redirecting clean air from the innermost orbits of the stratified rotating flow toward the outlet. This results in straightening out the airflow thereby adding additional pressure out of the clean air outlet of the system into the air inlet of the device downstream of the system. The use of additional pressure is useful in overcoming the air inlet restriction in the downstream device and is effective to increase filter change intervals for filters in the downstream device. In a disclosed embodiment, a plurality of de-swirl blades are provided centered in the outlet of the system for aerodynamically redirecting clean air from the innermost orbits of the stratified rotating flow toward the outlet.
According to a further feature of the improved powered air cleaning system, the motor-driven fan is a turbine-type fan with an impeller having a hub with blades thereon arranged in the flow path for rotation about an axis. The hub and the flow path at least in the area of the blades each have a progressively increasing diameter in the downstream direction of the flow path. In the preferred embodiment, the impeller is formed of an assembly of an injection molded blade component and an injection molded hub component. Features below the lower surface of blades on the blade component are formed on the hub component so that each component can be made using open and shut, two piece injection mold tooling.
The motor of the motor-driven fan is capable of rotating the fan at a speed on the order of 7,000 rpm. The motor is a variable speed motor which has an integrated motor controller for adjusting the speed of the motor and thereby the flow rate of clean air through the outlet of the system. In the case the outlet of the system is connected to an inlet of a device having variable airflow requirements, the air cleaning system further includes means for electronically signaling the controller as a function of the airflow requirements of the device for varying the speed of the motor and thereby the flow rate of clean air to the device in accordance with the airflow requirements.
The improved powered air cleaning system can be used to supply clean air to various devices, including, for example, a ventilation system and an internal combustion engine. Where the device is used on the air inlet of an internal combustion engine, the signals of the airflow requirements from the means for electronically signaling are based, for example, on at least the operating speed of the engine. With a ventilation system downstream of the powered air cleaning system, airflow requirements are electronically signaled by a pressurization switch (air pressure sensor) or filter differential pressure ΔP in the ventilation system.
An air cleaning method according to the invention comprises drawing particulate debris laden air into an air cleaning system with a motor-driven fan located in the system, forming a rotating flow of the debris laden air about an axis in a separator-ejector chamber of the system to stratify the flow with the heaviest particles in the outermost orbits of the rotating flow, aerodynamically redirecting clean air from the innermost orbits of the stratified rotating flow toward an outlet to provide a positive airflow pressure out of the outlet, and returning particulate debris laden air from the stratified rotating flow in the system to the environment. The redirecting according to an example embodiment includes using de-swirl blades mounted in the separator-ejector chamber to aerodynamically redirect the airflow toward the outlet to provide the positive airflow pressure out of the outlet.
According to a further feature, the method includes varying the speed of the motor-driven fan and thereby the flow rate of clean air through the outlet of the system as a function of the airflow requirements of a device being supplied with clean air by the system. Varying the speed includes sending an electronic signal from the device to the controller in the system which adjusts the speed of the motor-driven fan.
These and other features and advantages of the invention will become more apparent from the following detailed description of an example embodiment taken with the accompanying drawings.